1. Field of the Invention
The present invention relates to a charging member to be used in an electrophotographic apparatus and a method of producing the charging member, a process cartridge, and an electrophotographic image-forming apparatus.
2. Description of the Related Art
A charging member that abuts on an electrophotographic photosensitive member to charge the electrophotographic photosensitive member is generally formed so as to have a rubber-containing elastic layer in order that an abutment nip between the electrophotographic photosensitive member and the charging member may be sufficiently and uniformly secured.
In recent years, an additional improvement in durability has started to be required for an electrophotographic image-forming apparatus. To realize the improvement, its charging member has been demanded to exert stable charging performance over a long time period. Japanese Patent Application Laid-Open No. 2007-004102 proposes, as a charging member suppressing the fixation of toner or an external additive to its surface even after its long-term, repeated use, and showing stable charging performance over a long time period, a charging member including a surface layer containing a polysiloxane having an alkyl fluoride group and an oxyalkylene group.Meanwhile, in association with an increase in process speed of an electrophotographic image-forming apparatus in recent years, the time period for which its electrophotographic photosensitive member and charging member contact each other has started to become relatively short. The foregoing is disadvantageous to stably and reliably charge the electrophotographic photosensitive member. Specifically, as disclosed in Japanese Patent Application Laid-Open No. 2008-299255, it is said that the charging uniformity of the photosensitive member reduces, and in particular, a suppressing effect on a positive ghost reduces.
The positive ghost can be eliminated by removing residual charge on the photosensitive member after a transferring step through the performance of the so-called pre-exposure on the photosensitive member before the primary charging of the photosensitive member by the charging member. However, the introduction of pre-exposing unit into the electrophotographic image-forming apparatus is disadvantageous for a reduction in size of the electrophotographic image-forming apparatus. Accordingly, it can be said that the problem is preferably solved by improving the charging ability of the charging member itself.